Tunable antenna

Abstract

A tunable antenna includes an antenna element having a feed point at one end thereof, a feed line being connected to the feed point, and a switcher that switches the resonance frequency of the antenna element. The switcher is connected to the antenna element at a position that is at a distance other than (λm/4)×n from the one end towards another end of the antenna element, where λm represents the wavelength corresponding to any resonance frequency of the antenna element, and n is a positive, odd number.

The invention claimed is: 
     
       1. A tunable antenna, comprising:
 an antenna element including a feed point at one end thereof, a feed line being connected to the feed point; 
 a switcher configured to switch a resonance frequency of the antenna element; and 
 a ground mechanism connected to the antenna element, 
 wherein 
 the switcher is connected to the antenna element at a position that is at a distance other than (λ m /4)×n from the one end towards another end of the antenna element, where λ m  represents a wavelength corresponding to any resonance frequency of the antenna element, m is a natural number, and n is a positive, odd number, 
 the switcher is connected to the antenna element at a position that is at a distance of less than λ min /4 from the one end towards said another end of the antenna element, where λ min  represents a smallest wavelength among wavelengths corresponding to all resonance frequencies of the antenna element, 
 a length of the antenna element from the one end to said another end is L 1 =λ max /4, where λ max  represents a largest wavelength among the wavelengths corresponding to all resonance frequencies of the antenna element, and 
 the ground mechanism is connected to the antenna element at a position that is λ max /8 or less and less than λ min /4 from the one end towards said another end of the antenna element.